1. Technical Field
The entire disclosure of Japanese Patent Application No. 2007-210244, filed Aug. 10, 2007 and Japanese Patent Application No. 2008-198507, filed Jul. 31, 2008, are expressly incorporated by reference herein.
The present invention relates to an optical element having a polarizing beam-splitting function, as well as to a liquid crystal device and a display each using the optical element.
2. Related Art
Among optical elements having a polarized beam splitting function, there is known a polarized beam splitting element of a wire grid type. The wire-grid polarized-beam splitting element includes a large number of fine wires (such as fine lines made of aluminum) arranged on a surface of a glass substrate or the like. The wires are spaced apart from each other by a distance (a cycle) shorter than a wavelength of light. The wire-grid polarized-beam splitting element is characterized by excellent polarized-beam splitting capability, as well as high optical-damage threshold because of an inorganic material forming the element. Thus, use of the wire-grid polarized-beam splitting element in various optical systems is under consideration, as an alternative to conventional polarized beam splitting elements made of polymer. An application example of the wire-grid polarized-beam splitting element is a projection display such as a liquid crystal projector.
In the above projection display, the wire-grid polarized-beam splitting element is arranged on at least one of a front surface and a rear surface of a liquid crystal panel (a liquid crystal light valve). For example, to improve luminance of images displayed on a screen in the projection display, light having a relatively high intensity is input to the liquid crystal panel. However, in principle, the wire-grid polarized-beam splitting element almost totally transmits a TM-polarized component of incident light, whereas almost totally reflects a TE-polarized component of the incident light. Accordingly, there is a concern that the reflected light (the TE-polarized component) returns to the liquid crystal panel, thereby destabilizing operation of the liquid crystal panel. Additionally, such a concern is not restricted to the projection display and shared among various optical devices incorporating the wire-grid polarized-beam splitting element. In any of those optical devices, unnecessary reflected light generated on an optical path is undesirable.
JP-A-2002-372749 is an example of related art.